A conventionally known liquid-cooled-type cooling device of this type has a casing which, in turn, has a peripheral wall. The peripheral wall includes a first side wall and a second side wall positioned in opposition to each other. A cooling-liquid inlet is formed at one end portion of the first side wall, and a cooling-liquid outlet is formed at an end portion of the second side wall corresponding to the other end portion of the first side wall. In the casing, a parallel-flow-channel section is provided in an internal region located between the first side wall and the second side wall and between the cooling-liquid inlet and the cooling-liquid outlet. The parallel-flow-channel section includes a plurality of flow channels through which cooling liquid flows in the longitudinal direction of the first and second side walls. An internal region of the casing located upstream of the parallel-flow-channel section serves as an inlet header section communicating with the cooling-liquid inlet. An internal region of the casing located downstream of the parallel-flow-channel section serves as an outlet header section communicating with the cooling-liquid outlet. The inlet header section and the outlet header section have a rectangular cross section. Each of the inlet header section and the outlet header section has a uniform width along its overall length.
In the above-mentioned liquid-cooled-type cooling device, when the ratio of the width of the inlet header section and that of the outlet header section to the width of the parallel-flow-channel section is rendered sufficiently high, the distribution of flow velocities along the width of the parallel-flow-channel section becomes uniform, so that sufficient cooling performance is ensured.
However, recently, a reduction in the size of a liquid-cooled-type cooling device has been demanded. For this reason, the above-mentioned liquid-cooled-type cooling device encounters difficulty in having a sufficiently high ratio of the width of the inlet header section and that of the outlet header section to the width of the parallel-flow-channel section. As a result, the distribution of flow velocities along the direction of width of the parallel-flow-channel section becomes nonuniform, raising a problem of deterioration in cooling performance in a region of the parallel-flow-channel section where the flow velocity drops.
In order to solve the above-mentioned problem, Patent Document 1 proposes a liquid-cooled-type cooling device having a casing configured in the following manner. The casing has a peripheral wall including a first side wall and a second side wall positioned in opposition to each other. A cooling-liquid inlet is formed at one end portion of the first side wall, and a cooling-liquid outlet is formed at an end portion of the second side wall corresponding to the other end portion of the first side wall. In the casing, a parallel-flow-channel section is provided in an internal region located between the first side wall and the second side wall and between the cooling-liquid inlet and the cooling-liquid outlet. The parallel-flow-channel section includes a plurality of flow channels through which cooling liquid flows in the longitudinal direction of the first and second side walls. An internal region of the casing located upstream of the parallel-flow-channel section serves as an inlet header section communicating with the cooling-liquid inlet. An internal region of the casing located downstream of the parallel-flow-channel section serves as an outlet header section communicating with the cooling-liquid outlet. The cross-sectional flow-channel area of the inlet header section reduces in a direction from a side toward the cooling liquid inlet to a side toward the second side wall. The cross-sectional flow-channel area of the outlet header section reduces in a direction from a side toward the cooling-liquid outlet to a side toward the first side wall. The shape of the inlet header section and the shape of the outlet header section are symmetrical to each other with respect to the direction of width of the parallel-flow-channel section.
However, even in the liquid-cooled-type cooling device described in Patent Document 1, the distribution of flow velocities of all the flow channels is not sufficiently uniform. As a result, there arises a region of the parallel-flow-channel section where the flow velocity drops, and cooling performance in the region deteriorates. Furthermore, flow resistance may possibly increase.
Patent Document 1:
Japanese Patent Application Laid-Open (kokai) No. 2006-295178